Table 1.

Included mobile phone intervention studies

First author, year	Study design & duration	Sample characteristics	Vulnerable/disadvantaged classification	Intervention characteristics	Intervention tailoring	Control group	Glycemic control
Agboola, 2016 [52]	Two-arm randomized control trial 6 months.	126 English- or Spanish-speaking patients with T2D (n = 64 intervention, n = 62 control) from four health centers in MA, USA. Mean age 51 years, 52% female, with baseline A1c 8.7%.	50% high school education/GED or less	Text to Move incorporates physical activity monitoring and coaching to provide automated and personalized text messages to help patients with T2D achieve their physical activity goals.	Text messages tailored to participant preferred language goal, demographic, and behavioral information including stages of change	Received pedometers and usual care.	A1c decreased by 0.43% in the intervention group (p = .01) compared to 0.21% (p = .29) in the control group, but the between-group difference was not significant.
Arora, 2014 [53]	Two-arm randomized controlled trial 6 months.	128 patients with T2D (n = 64 intervention, n = 64 control) from a safety-net hospital in Los Angeles, CA, USA. Mean age 51 years, 82% female, with baseline A1c 10.1%.	87% Latino, 9% African American	TExT-MED sends unidirectional daily text messages delivering education/motivation, medication reminders, healthy living challenges, and trivia questions with answers sent 1 h after these messages.	None	Usual care	A1c decreased by 1.05% in the intervention group compared to 0.60% in the control group (Δ 0.45; 95% CI −0.27 to 1.17), but the between-group difference was not significant. Among Spanish-speaking patients (n = 92), the intervention group improved (1.20%) significantly more than the control group (0.40%; Δ 0.80).
Bell, 2012 [54]	Two-arm randomized controlled trial 6 months. (tracked change for 1 year)	65 patients with T2D or T1D (n =32 intervention, n = 33 control) from a military medical center in Washington, D.C., USA; Mean age 58 years, 45% female, with baseline A1c 9.3%.	58% African American	Intervention sends daily, asynchronous unidirectional 30- to 60-s videos (out of 540 videos) in random order to broadband-enabled mobile phones. Videos covered diabetes self-care topics (e.g., health eating, being active, monitoring), and could be viewed multiple times for 24 h upon receipt.	Videos sent at user-determined time of day	Usual care	A1c decreased more in the intervention group compared to the control group (0.02% difference over 12 months., p < .01), especially in the first 3 months. The rate of decline was greatest among people who received and viewed >10 videos per month.
Capozza, 2015 [55]	Two-arm randomized controlled trial 6 months.	93 patients with T2D (n = 58 intervention, n = 35 control) from primary care clinics in Salt Lake City, UT, USA. Mean age 53 years, 61% female, with baseline A1c 9.1%.	65% of participants recruited from clinics serving mostly low-income patients	Care4Life sends 1–7 daily unidirectional and bi-directional text messages written at the 5th grade reading level related to diabetes education and health improvement, and access to a web-based portal for viewing trends in biometric and behavioral bi-directional text messages responses.	Type, timing, and frequency of texts; option to turn off texts any time by texting "stop"	Usual care	A1c decreased in the intervention group and in the control group (reductions/p values not provided). There were no between-group differences at 3 or 6 months.
Cho, 2011 [56]	Two-arm randomized controlled trial 3 months.	71 patients with T2D (n = 36 intervention, n = 35 control) from Chung-ju City, South Korea. Mean age 64 years, 61% female, with baseline A1c 8.0%.	100% rural	Nurses measure blood glucose with personal data assistant glucometers and upload these values along with patients' diet, exercise, and medications for remote physician review and individualized self-care prescription delivered face-to-face by the nurse.	Individualized self-care prescription and drug modification based on blood glucose values and current self-care behaviors.	Nurse measures blood glucose with personal data assistant glucometer and provides general diabetes education, but does not send glucose values to the physician for individualizing the self-care prescription	A1c decreased in the intervention group by 0.50% (p < .01) at 3 months. A1c did not decrease in the control group. Between-group differences not presented.
Fortmann, 2017 [57]	Two-arm randomized control trial 6 months.	126 patients with T2D (n = 63 intervention, n = 63 control) from San Diego, CA, USA. Mean age 48 years, 75% female, with baseline A1c 9.5%.	100% Latino 75% uninsured	Dulce Digital sends text messages to participants containing educational messages, medication reminders, and blood glucose monitoring prompts. Blood glucose monitoring texts encouraged participants to text message in their next observed value	Texts tailored for language.	All participants viewed an educational video and received a blood glucose meter, testing strips, and instructions on use. Control group also received usual care	Dulce Digital intervention group exhibited greater improvement in A1c across time compared with control group (p = 0.03).
Haddad, 2014 [58]	Non-experimental pre-post design 6 months.	50 newly-diagnosed patients with T2D from a teaching hospital in Basra, Iraq. Of the 42 patients who completed the study, mean age 51 years, 71% female, with baseline A1c 9.3%.	100% LMIC	Intervention sends one weekly, unidirectional text messages reminding users about one of five aspects of diabetes management: diet, medications, complications, blood glucose monitoring, and clinic attendance.	Text messages sent at user-determined day/time ofthe week.	N/A	A1c decreased in the intervention group by 0.70% (p <.001).
Islam, 2015 [59]	Two-arm randomized control trial 6 months.	236 patients with T2D from Bangladesh Institute of Health Sciences in Dhaka, Bangladesh. Mean age 48 years, 54% female, with baseline A1c 8.4%.	100% LMIC	Intervention group received daily text messages based on the principles of behavioral learning theory.	None.	Usual care	A1c decreased by 0.85% for intervention group and 0.18% for the control group (p <0.001).
Katz, 2012 [60]	Non-experimental pre-post design 12 months.	32 patients with T2D from a community health center in Washington, D.C., USA. Mean age 39 years, 97% female, with baseline A1c 8.0%.	100% African American	WellDoc is an interactive platform for patients and healthcare providers to track blood glucose and receive real-time feedback and diabetes information. Case managers monitor patients' dashboards and send weekly personalized messages.	Case managers send weekly personalized messages based on blood glucose uploads.	N/A	Success in receiving a standard-of-care A1c test declined over the study period, regardless of level of intervention engagement. Because blood testing was not required at the end of the study, A1c change could not be examined.
Lim, 2016 [61]	Two-arm randomized controlled trial 6 months.	100 patients with T2D (n = 50 intervention, n = 50 control) from Seoul National University Bundang Hospital in South Korea. Mean age 65 years, 25% female, with baseline A1c 8.0%.	53% <high school education	U-healthcare uses a glucometer and physical activity monitor worn at the waist. Each connects to a public switched telephone network via Bluetooth to transfer results to a server in the u-healthcare center. Tailored messages are automatically sent to users' mobile phones in response to results. Participants were recommended to measure their blood glucose level at least 8 times per week and wear the physical activity monitoring device.	Feedback text messages tailored to results of self-monitoring of blood glucose levels and physical activity data relative to each participanťs recommended activity level set by an exercise physiologist.	Both groups received diabetes education for 1 h each at baseline, 3 and 6 months. Control group participants were recommended to measure their blood glucose level at least 8 times per week and wear a non-connected physical activity monitoring device.	A1c was significantly decreased in the intervention group, as compared to the control group, at 3- and 6-month follow-up (p < .05). At 6 months, decreases were 0.7% in the intervention group as compared to 0.2% in the control group. A greater proportion ofintervention group participants had A1c < 7.0% (26% vs. 12%, p < .05).
Nundy, 2014 [62]	Pre-post quasi-experimental design 6 months.	348 patients with T2D or T1D (n = 74 intervention, n = 274 control) from an academic medical center in Chicago, IL, USA Mean age 53 years, 52% female, with baseline A1c 7.6%.	66% African American	CareSmarts is a theory-driven mobile intervention that sends unidirectional and bi-directional text messages to educate about diabetes, prompt self-care, and ask about self-care needs structured in two-week modules that users can experience at their own pace. Nurses monitor and respond to users' text message responses.	The contents of the messages users receive are modified through software every 2 weeks as needed, based on users' interactions wi the system.	Usual care	A1c decreased in the intervention group by 0.70% (p < .01) at 6 months. A1c did not decrease in the control group. Between-group differences not presented.
Ratanawongsa, 2014 [63]	Four-arm stepped wedge design ~6 months. (27 weeks)	252 patients with T2D or T1D (n = 127 intervention, n = 125 control) from San Francisco, CA, USA. Mean age 56 years, 74% female, with baseline A1c 7.0%.	Recruited from publicly funded clinics 61% Asian/Pacific Islander 63% ≤$20 K income	Automated telephone self-management support and health coaching intervention. Out-of-range responses triggered callbacks within 3 days from language-concordant health coach, for collaborative goal-setting to form patient-centered action plans.	Automated calls tailored for language (English, Spanish, or Cantonese), literacy, and culture.	Usual care	No significant changes in A1c, within or between groups.
Wayne, 2014 [64]	Non-experimental pre-post design 6 months.	21 patients with T2D from a community health center in Toronto, Canada. Mean age 56 years, 57% female, with baseline A1c 7.6%.	14% Latino, 14% African, 14% Caribbean, 14% South Asian	Health Coach app supports multi-channel communications between users, health coaches, and supportive family members, and supports tracking health behaviors (e.g., exercise, diet) and self-monitoring health data (e.g., blood glucose, mood, and energy).	A human health coach and patient collaboratively create a personalized wellness plan based on electronic monitoring entries and physician and dietician medication and dietary guidelines, respectively.	N/A	A1c decreased in the intervention group by 0.28% (p = 0.05) at 6 months. Patients with uncontrolled baseline A1c (n = 12) experienced the greatest A1c improvement (0.43%, p = .04).
Wayne, 2015 [65]	Randomized control trial 6 months.	97 patients with T2D (n =48 health coaching with mobile phone support, n = 49 health coaching without mobile phone support) from two health centers in Toronto, Canada. Mean age 53 years, 72% female, with baseline A1c 8.8%.	5% African, 40% Caribbean, 9% Hispanic	With health coach assistance, clients determined health-related goals and monitored daily progress. The health coach monitored participanťs mobile phone input and directed immediate attention to episodes of desirable progress, relapse, and resistance. Intervention group could track/monitor their meals, exercise, blood glucose, and mood and communicate with the coach any time through the platform.	A human health coach and patient create a personalized wellness pla based on electronic monitoring entries.	Both groups had access to a health coach; however, n control group did not have smartphone interaction. Both groups also had access to decision support and action support through the health coach, as well as had access to the Exercise Education Program. Control group participated in verbal discussion of meals, exercise, blood glucose, and mood.	A1c decreased in the intervention group by 0.84% (p = .001) and in the control group by 0.81% (p = .001) over 6 months. No significant between-group changes. Intervention group did achieve an accelerated A1c reduction, leading to a significant between-group difference at 3 months (p = .03).